1. Field of the Invention
The present invention relates to information recording devices and information output devices, and more particularly to an information recording device which records digital information inputted in the on-line, off-line or broadcasting form on a copy target recording medium with its quality deteriorated, and an information output device for externally outputting the information with its quality deteriorated.
2. Description of the Background Art
In a conventional information recording device, when video information, audio information or video-audio information digitally recorded on a copy source recording medium is copied on a copy target recording medium, the video-audio information of the copy has completely the same quality as the original video-audio information. Referring to the figure, the procedure for making a copy in the conventional information recording device will now be described.
FIG. 6 is a block diagram showing the structure of the conventional information recording device. In FIG. 6, the information recording device 60 includes an original recording medium 61, an information reading portion 63, an information writing portion 64 and a copy target recording medium 65.
The original recording medium 61 has video-audio information (original) 62 which is digital information recorded thereon. The video-audio information 62 has the recording system including auxiliary information such as header information, error correction information, etc. in addition to video information and/or audio information, as MPEG (Motion Picture Experts Group) 2 stream format, for example.
The information reading portion 63 reads the video-audio information (original) 62 from the original recording medium 61 in order according to its recording system. The video-audio information (original) 62, which is digital information, presents a train of "0's" and "1's". The information writing portion 64 records the video-audio information (original) 62 onto the copy target recording medium 65 in the order read out by the information reading portion 63. At this time, if the digital information read is "0", for example, it is of course recorded on the copy target recording medium 65 as "0". The information reading portion 63 and the information writing portion 64 proceed with the processing as above to produce video-audio information (copy) 66 having the same quality as the video-audio information (original) 62 on the copy target recording medium 65.
The use of the information recording device 60, however, allows anybody to easily make a copy of the video-audio information, or the like, regardless of intention of its copyright holder. Furthermore, the produced copy has the same quality as the original video-audio information. This may lead to an illegal sale of the copy on the market, producing -the problem that the copyright can not be effectively protected.
The technique for protecting the copyright above includes SCMS (Serial Copy Management System) provided in a deck for DAT (Digital Audio Tape) etc. and "ANTI-COPY SYSTEM" disclosed in U.S. Pat. No. 4644422.
As is well known, the SCMS mentioned above is a system for preventing a copy based on the digital information recorded on an original recording medium from being taken over like an endless chain. More specifically, when copy permitted/unpermitted information, which is indicative of whether copying is permitted or not permitted, indicates that copying is unpermitted, it prohibits copying the digital information. Thus unpermitted copying is prevented. However, the present invention is intended to protect copyrighted works by deteriorating the quality of digital information, so its basic point of view is different.
The above-mentioned "ANTI-COPY SYSTEM" superimposes deterioration signal having a frequency over the man's audible range on audio information which is the analogue form. The audio information with the deterioration signal superimposed is recorded on an original recording medium. When making a copy of such audio information, it is recorded onto a copy target recording medium with high-frequency signal from a bias oscillator further superimposed thereon. Accordingly, when the audio information recorded on the copy target recording medium is reproduced, the deterioration signal and the high-frequency signal interact with each other to generate higher harmonic which is unendurable to hear. Thus the ANTI-COPY SYSTEM prevents copying onto a copy target recording medium.
According to the aforementioned ANTI-COPY SYSTEM, however, it is possible to reproduce the audio information recorded on the copy target recording medium, but it can not be utilized. That is to say, it prevents personal usage which is not subject to the force of the copyright. Accordingly, it differs from the present invention which is intended to protect the copyright while permitting copying, and its problem solving means also differs.